I am trying to write a basic code for (tower arithmetic), atleast thats what its called in my language.
I am new, so I need some help
Im gonna explain how it works:
you have to input 2 numbers number1, number2
those have to multiply result=(number1 * number2)
the result has to be multiplied with number2 again and +1 on number2 number1=(result * (number2+1))
this has to loop for 5 times
I hope you understand what I mean and someone can help me
#!/usr/bin/env bash
set -e # stops execution on first error
set -x # adds tracing of execution steps
read -p "Number 1: " number1
read -p "Number 2: " number2
result=$((number1 * number2))
for i in $(seq 1 5)
do
result=$((result * $((number2 + i))))
done
echo "Result: $result"
Related
This question already has answers here:
Brace expansion with variable? [duplicate]
(6 answers)
Closed 3 years ago.
I need to get user input for a number and then write a name row by row in linux terminal that much amount of times that user inputed. Example if I lets say chose a number 2 the program will write Name 2 times row by row. I wrote some code but I cant figure where is the mistake. I think its the loop where the mistake is.
echo "Please enter a number "
read $number
for value in {$number}
do
echo "Name"
done
To read input and save it into a variable named number, do:
read number
To get the value of number, do $number or ${number}. Remove the { } in the {$number} or shift $ with {.
Just do:
echo "Please enter a number "
read number
if ! test "$number" -gt 0 2> /dev/null; then
echo "You must enter an integer greater than 0" >&2
exit 1
fi
yes Name | sed ${number}q
But don't prompt for the number. Take it as a command line argument, and just do
yes Name | sed "${1}q"
Let sed generate the error message if the parameter is invalid.
The trouble with your loop is that for value in $number takes the string $number and breaks it on whitespace (depends on IFS, actually, but let's not get bogged down by details) and iterates over each value. That is, if $number is the string 1 3 dog 5, then the loop will iterate 4 times with $value taking the values 1, 3, dog, and 5. If $number is 7, then the loop iterates exactly once. You could do for((i=0; i < $number; i++)); do ..., but that does not generate any useful error message if $number is not an integer.
This question already has answers here:
Why equal to operator does not work if it is not surrounded by space?
(4 answers)
How to compare strings in Bash
(12 answers)
Multiplication on command line terminal
(8 answers)
Closed 3 years ago.
I am in the very early stages of learning Unix scripting. I've written a Bash script which does not generate any errors, but clearly has a logic error, as the IF test always gives the same response.
I have tried various variations on the theme of my IF, but still end up with the same result.
#!/bin/bash
declare -i number1
declare -i number2
declare -i total
declare operation
echo "Enter a, s, m or d for add, subtract, multiply or divide"
read operation
echo "Enter number 1"
read number1
echo "Enter number 2"
read number2
echo "operation="$operation
if [ $operation=='m' ]
then
total=$number1*$number2
elif [ $operation=='a' ]
then
total=$number1+$number2
elif [ $operation=='d' ]
then
total=$number1/$number2
elif [ $operation=='s' ]
then
total=$number1-$number2
fi
echo $number1 " multiplied by " $number2 " equals " $total
exit 0
It doesn't matter whether I enter a, s or d (or indeed m) in response to the first prompt, my script always does a really nice multiplication... The line
echo "operation="$operation
correctly shows the operator I've requested.
Any ideas what I've done wrong?
Many thanks
You need to add spaces around all the ==. That's it. Instead of
if [ $operation=='m' ]
you should have:
if [ $operation == 'm' ]
I'm making a bash script in Vim editor for my operating systems fundamentals class, and I am having an extremely simple yet frustrating error occur where I cannot add variables together and set the sum to another variable. I've tried numerous formats to get this done, however it either prints out each value or a ": not found" error. Here is the code I have so far, I simply want to set the sum of the values for each test into the variable 'finalgrade' and print the output.
echo "Enter assignment mark (0 to 40): " ; read assignment
echo "Enter test1 mark (0 to 15): " ; read test1
echo "Enter test2 mark (0 to 15): " ; read test2
echo "Enter final exam mark (0 to 30): " ; read exam
finalgrade = $assignment + $test1 + $test2 + $exam
echo "Your final grade is : "$finalgrade
This is an example of what I get when I run it:
$ sh myscript
Enter assignment mark (0 to 40):
1
Enter test1 mark (0 to 15):
2
Enter test2 mark (0 to 15):
3
Enter final exam mark (0 to 30):
4
myscript: 5: myscript: finalgrade: not found
Your final grade is :
I instead expected the last line to be:
Your final grade is : 10
Thanks,
This line
finalgrade = $assignment + $test1 + $test2 + $exam
will not perform any math. Googling "bash math" will provide various ways to do this but here is one;
finalgrade=$((assignment + test1 + test2 + exam))
It is worth noting that your actual problem is that you have spaces beside the assignment = which causes bash to interpret this as a command "finalgrade" (not found) instead of an assignment. Variable assignments must not have spaces beside the =.
I am trying to calculate 20% of a where a is input by the user.
echo "Please enter your basic salary"
read a
#HRA
b=`expr (20 / 100)\* $a)`|bc
echo HRA is:$b
What's wrong in this expression, which is generating an error message?
The first problem is that you want to just pass the expression into bc for evaluation, so use echo rather than expr.
Secondly, the order of evaluation you have is going to calculate 20/100 as an integer first, which will be 0, then multiple the salary by that, resulting in 0. Reordering the calculation will resolve that.
So the following should work:
echo "Please enter your basic salary"
read a
#HRA
b=`echo $a " * 20 / 100"|bc`
echo HRA is:$b
Alternatively, if you prefer to use expr rather than bc, you can escape the problem characters to make this work:
echo "Please enter your basic salary"
read a
#HRA
b=`expr $a \* 20 \/ 100`
echo HRA is:$b
You can use let operator also in bash
#!/bin/bash
echo "Please enter your basic salary"
read a
let b=$a*20/100
echo HRA is:$b
I am trying to make a switch statement to work in tcsh but I am not sure why it is not working. I am displaying a menu on the screen and if the option is selected it shows the price and then goes back to the top and repeats until the exit option is selected.
#!/bin/csh
clear
echo -n "Petes A Pizza "
echo -n " Menu "
echo -n " "
echo -n " Make a selection "
echo -n " "
echo -n " A. Speciality Pizza "
echo -n " B. Veggi Lovers Pizza "
echo -n " C. Meat Lovers Pizza "
echo -n " D. Hawaiian Pizza "
echo -n " E. Cheese Pizza "
echo -n " F. Exit "
set a = $<
switch ($a)
case [A] :
set A = ((7.99 + 0.07))
echo $A
sleep 5
goto top
case [B] : #they choose option 2
set B = ((8.99 * 0.07) + 8.99)
echo $B
sleep 5
goto top
case [C] : #they choose option 3
set C = ((6.99 * 0.07) + 6.99)
echo $C
sleep 5
goto top
case [D] : #they choose option 4
set D = ((8.49 * 0.07) + 8.49)
echo $D
sleep 5
goto top
case [E] : #they choose option 5
set E = ((3.99 * 0.07) + 3.99)
echo $E
sleep 5
case [F] :
exit 0
breaksw
endsw
end
Here are a few suggestions that should be enough to help you get it working.
Change #!/bin/csh to #!bin/csh -f. This tells the shell not to read your ~/.cshrc file, which saves time and can avoid confusion. (If you accidentally write code that depends on aliases you've defined in your .cshrc, for example, your script won't work for anyone else.)
If you must clear the screen, the clear command is the way to do it -- but why? If I want to clear my screen before running your script, I'll do it myself, thank you very much. If I have information on my screen that I don't want to lose, I'll be annoyed when your script decides to erase it for me.
Change all the echo -ns to just echo. The -n option tells echo to print its output without a trailing newline; your entire menu will be printed on one line.
The square brackets in your case labels are unnecessary. case A : means the same thing as case [A] :. Note that you're requiring the user to provide input in upper case, which may be inconvenient.
set A = ((7.99 + 0.07))
...
set B = ((8.99 * 0.07) + 8.99)
These are inconsistent. It looks like you're trying to compute a base price plus 7% sales tax. For case B, a simpler expression for that is 8.99 * 1.07.
csh doesn't recognize this (( ... )) syntax; I wonder where you got the idea that it does. csh can do arithmetic using the # command:
# x = 2 + 2
# x ++
but it only operates on integers. The bc command can do floating-point calculations. You could write something like:
set B = `echo 'scale=5; 1.07 * 8.99' | bc`
Or, more simply:
set B = `echo '1.07 * 8.99' | bc -l
but bc -l may give you more digits than you want. man bc for more information on the bc command, its syntax, and how it works. Remember that the values of csh variables are strings, not numbers.
(I'm not sure bc is the best tool for this job.)
Finally, csh is not the best language for writing scripts. I've been using it for more years than I care to admit, and I sometimes have to resort to trial and error to find out how a given piece of syntax will behave; the syntax is poorly defined in many cases, and the man page doesn't always clear things up.
Suggested reading: "Csh Programming Considered Harmful", by Tom Christiansen.